The disclosure generally relates to an avalanche photodiode and, more particularly, to a biasing voltage generating circuit of an avalanche photodiode and related control circuit.
Avalanche photodiodes are widely applied in many optical applications with higher sensitivity requirements, such as optical communication, optical distance measurement, etc. Ideally, a reverse biasing voltage applied to the avalanche photodiode should be designed to be close to but does not exceed the breakdown voltage of the avalanche photodiode in order to obtain better signal gain.
The signal gain of the avalanche photodiode has a very high correlation with both the magnitude of the reverse biasing voltage applied to the avalanche photodiode and the temperature. Therefore, a lookup table for recording the correlation between the temperature and the required reverse biasing voltage of the avalanche photodiode should be pre-stored in a conventional biasing voltage generating circuit of the avalanche photodiode. Due to the process deviation, however, different avalanche photodiodes have different correlations between the temperature and the required reverse biasing voltage.
In the conventional biasing voltage generating circuit, a boost power converter is typically employed to convert an input voltage into the required reverse biasing voltage of the avalanche photodiode. To maintain the stability of the reverse biasing voltage, the conventional biasing voltage generating circuit requires a DAC (digital-to-analog converter) to generate an analog signal according to the control values generated by a control circuit, and couples the analog signal to a voltage-divided signal generated by external divider resistors to from a feedback signal required for the operations of the boost power converter.
However, the circuit structure of the DAC is complex, and thus the DAC requires occupying more circuit area and higher hardware cost. Therefore, the entire circuitry architecture for the conventional biasing voltage generating circuit to control the boost power converter to generate the required reverse biasing voltage of the avalanche photodiode is too complex and costly.